Table of Contents

5.2.1 Traffic Data

Traffic data is generally provided as the total traffic volume on the road in both directions, and not for individual lanes, shoulders etc. Traffic volume may be given as:

  • AADT, which is the most common method used by road agencies, being the total volume of traffic passing a roadside observation point over the period of a calendar year, divided by the number of days in that year (365 or 366 days). The percentage of commercial vehicles within the total volume of traffic is also reported, and can be further broken down into different heavy vehicle types as per the Austroads vehicle classification system.
  • a 12-hour or 24-hour count at a particular date or time. Road agencies can generally provide factors to convert the 12 and 24-hour counts to AADT. For example, on medium to low traffic roads, a factor of the order of 1.25 to 1.30 is typically used to convert 12-hour counts to AADT. For a freeway or other very busy urban road, with a large percentage of traffic travelling at night, the factor is generally 1.45 to 1.50, and can be as high as 2.0 in some instances.
  • v/l/d, generally on multiple-lane urban and rural roads where the traffic count is taken for individual lanes.

As this sprayed seal design method uses v/l/d as its basis, traffic data provided in other formats should be converted to this.